The official website announced an "Eggstravaganza" event.
From today at 1 P.M. PDT until April 20, 2017, at 1 P.M. PDT, a greater variety of Pokémon can now be found in 2 km Eggs and each egg will will give more candy than usual.
Throughout this event, players will get double experience and Lucky Eggs are 50% cheaper.

Trainers,

Lace up your walking shoes and get ready to put a spring in your step—the Pokémon GO Eggstravaganza is nearly here! From 1:00 P.M. PDT on April 13 to 1:00 P.M. PDT on April 20, 2017, a greater variety of Pokémon can now be found in 2 km Eggs, so get cracking and see what you find! Your Egg-venture doesn’t stop there, though—you’ll also earn more Candy for every Egg you hatch!

Throughout this Eggstravaganza, you’ll also level up even faster with double XP! Combine this Egg-cellent bonus with a Lucky Egg, and you’ll earn four times the XP you normally would. To make this Eggstravaganza even sweeter, Lucky Eggs will be 50% off in the in-game shop!

Get out there, hatch some Eggs, and share your stories with us using #PokemonGO on your favorite social media channels.